Fire regime and spatial distributions of leaf litter- and ground-dwelling ants (Hymenoptera: Formicidae) across the tapia woodland of Madagascar

Abstract

The Central Highland of Madagascar has a native vegetation formation known as tapia woodland that is able to withstand regular fires. However, the ant fauna of this habitat remains poorly understood. This study compares the distribution of ant species in recently burned (<1 yr since fire) and unburned (>4 years since fire) tapia vegetation, which is dominated by the tapia tree Uapaca bojeri (Phyllanthaceae). Three quantitative inventory methods-mini-Winkler, monolith, and pitfall traps-were employed along a 200-m transect with 20 plots per site. In total, 155 ant species were collected, comprising 146 native species (95%) and 8 introduced species (5%). A statistical analysis revealed no significant differences in species richness between the burned and unburned plots for each method. Divergent patterns in species composition were observed between paired burned and unburned plots across 3 sites: Ambositra (56 vs 64), Ibity (23 vs 42), and Itremo (60 vs 59). Aggregating data from paired burned and unburned plots increased the species richness per locality. At Itremo, the combined species richness was 86, compared to 59 in unburned plots alone. Similarly, at Ibity, despite fire negatively impacting vegetation structure, the combined species richness was 51, versus 43 for unburned sites. Introduced ant species did not significantly differ between burned and unburned sites, with at least 4 species recorded at each tapia formation. The discovery of ground-nesting Camponotus andrianjaka, the first ant species in Madagascar found to have repletes, indicates an adaptation to arid environments and a possible strategy to escape fire.